[vorbis-dev] comparison of beta2 and beta3 encoder quality

[Segher Boessenkool]

Attila Padar wrote:
> 
> Hi,
> I encoded some songs into 350 kbit/s with beta2 and beta3 too,
> and I don't know why, but it seems the b2 sounds better (makes a
> better quality ogg file)...

On some music, beta2 sounds better (imho); on most, beta3 does. Note
I'm encoding at lower bitrates than you are, so maybe beta2 is better
on most for 350kbps.

> The b2 contains more the b3 contains less high sounds.
> And with the b3, the size of file is smaller with 4-5%...

That's normal: Vorbis doesn't try to get the bitrate you request, it's
just an indication for how exactly it does the coding (which psycho
acoustic parameters to use).

> Do you know this problem, or do you think so, that the sound quality
> is good (or better in the b3) ??

Better, most of the time.

> Please be carefull with the floating point calculations!

Yes, they will attack when you least expect-em to ;-)

> Change them only then, if it seems the new solution/routine
> is surely perfect (better or same quality like in original).

What makes you think this is not what happened between beta2 and
beta3?

> Please - if you can - don't use pre-calculated floating point numbers
> (i.e.: 0.34563), calculate every numbers in the program (with sin/cos/exp
> function and with integer values). Somehow and somewhere the pre-calculated

.034563 is 17 (and a half) bit of precision; on more digit and it's the best
you'll ever need. Input and output is only 16 bit pcm; that's 15 bits of
precision. Having 20 bits for intermediate calculations is all you need,
provided your algorithms are numerically stable. If not, you lose anyway.

> numbers were also calculated...
> 
> Please use a 'typedef' for the floating point precision too (i.e. typedef
> float ogg_float_t), but I would be happy if you would use 'bouble' by
> default...

What's a bouble? Or do you mean double? The cahnge from double to float was
not exactly entirely accidental, or not well-thought...

> Or at least, the possibility of the more precision and more clear sound.

You can have better precision if you like, but it won't give you better
sound.

> So, the Ogg Vorbis is very good, maybe with these modifications it could
> be perfect too.

It will never be perfect, sorry to burst your bubble, but real life
stinks.

Ciao,

Segher
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